One interesting idea could be exploring the complex relationships Harry has to re - evaluate. For example, his friendships might be strained as he changes sides. Another aspect could be how his view of the magical world's power structures alters. He might start to see the other side's motives in a different light, which could lead to some unexpected alliances.
Obviously, Harry Potter himself is the central character in this type of fanfiction. Then there are often characters like Voldemort or his Death Eaters, as they are the ones Harry would be changing sides to. Bellatrix Lestrange could be a key figure in trying to persuade Harry or manipulate him into joining their side.
The Death Eaters themselves would be affected in an interesting way. Some might welcome Harry with open arms, but others might be suspicious of his sudden change of sides. They might fear that it's a trick by the Order. And within Hogwarts, the students would be in turmoil. Those who idolized Harry would be heartbroken and confused, and there could be a split among the student body depending on who believes Harry's new stance.
Perhaps Harry discovers some long - hidden family secrets that make him believe that the so - called 'good side' has been wrong all along. He might find out that his family has a connection to the Dark Arts that was misrepresented by Dumbledore and others. This newfound knowledge could cause him to change sides and try to rewrite the wizarding world's view of good and evil.
The character development may start with Harry's doubts. He begins to question the side he was on, which leads to his decision to change. As he moves to the other side, he has to adapt to new values and beliefs. This forces him to grow and re - evaluate his past actions.
Another plot could involve Harry being influenced by a family connection he discovers to a Death Eater. This newfound relation makes him reevaluate his beliefs and he starts to see the Death Eaters as more than just pure evil. He might think that by joining them, he can reform them from the inside.
His relationship with his family would be severely strained. His parents, who were loyal to the Dark side, would be shocked and disappointed. They might even try to persuade him to come back, which could lead to a lot of family drama.
Another possibility is that Draco falls in love with a character from the opposing side. His love could be so strong that it overrides his loyalty to his original side, leading him to change. For example, if he falls for a Gryffindor, he might start to see things from their perspective and gradually shift his allegiance.
Fanfiction about Sanders Sides Dark Sides often explores the complex and darker aspects of the characters. It can provide a different perspective on their personalities and relationships. For example, it might delve into how the Dark Sides influence the main characters in unexpected ways.
One popular trope is the 'Redemption Arc' for the Dark Sides. Writers often like to explore if and how these darker characters can find a way to be more positive.